1. Field of the Invention
The present invention relates to a focusing apparatus that performs focusing a phase difference method.
2. Description of the Related Art
Previously, when an auto-focusing (AF) is performed using an image signal obtained from an image pickup element (an image pickup surface) of an image pickup apparatus, commonly an AF control of a contrast method (TVAF) is performed. In the AF control of the contrast method, since the continuity of AF evaluation values is required, an exposure value during the AF control needs to be fixed (maintained) so as to be a value obtained before starting the AF control. Japanese Patent Laid-Open No. H8-265629 discloses a configuration in which an error determination of an in-focus state caused by the AF evaluation value obtained by the contrast method that is varied in accordance with a state of an exposure is prevented.
However, in the configuration disclosed in Japanese Patent Laid-Open No. H8-265629, the AF evaluation value of the contrast method is affected by an output of an image signal, and the continuity of the AF evaluation values need to be considered. Therefore, Japanese Patent Laid-Open No. H8-265629 focuses on the exposure value which is fixed during the AF control.
On the other hand, an AF control by a phase difference method uses an AF evaluation value based on a shift amount of image signals, and it is preferred that the AE control is appropriately performed in order to obtain an exact AF evaluation value. Therefore, when the AF control is performed by combining the phase difference method and the contrast method or a phase difference detection is performed by switching a plurality of ranging regions by the phase difference method on an image pickup surface, the exposure value needs to be control in accordance with each method.